1. Field of the Invention
The present invention relates to a boosting mechanism for a stapler which enables one to drive out a staple by weak force.
2. Description of the Related Art
Where something is stapled with a staple of a stapler, if the size of the staple is large or the number of staples or sheets of paper to be stapled is increased, it is necessary to press down a handle member by strong force to drive the staple into the sheets. Accordingly, handling of the stapler by women or children is not easy.
To cope with this, a stapler with a boosting mechanism as shown in FIG. 7 is presented. In the boosting mechanism, a handle member 21 and a driver arm 22 for holding a driver are separately provided. The handle member 21 is pivotally mounted on a shaft 23 positioned somewhat rearward of a mid position of the driver arm 22. A shaft 25, which is provided to the driver arm 22 at further rearward of the shaft 23, is engaged with an elongated hole 26 formed in the handle member 21. When the handle member 21 is pressed down, strong force acts on the driver arm 22 according to the principles of the lever. Accordingly, the staple may be reliably driven with small driving-out force even if the staple is large in size or driven out into a thick sheet.
The principles of the lever is utilized in the stapler. For this reason, a point at which the shaft 25 of the clincher arm comes into engagement with the elongated hole 26 of the handle member serves as a point of action.
The inner edge of the elongated hole 26 receives a great force from the shaft 25. When the shaft 25, circular in cross section, engages with the inner edge of the elongated hole 26, the former linearly contacts with the latter. Accordingly, a force acting on the inner edge of the elongated hole 26 is considerably large. In this condition, the inner edge of the elongated hole 26 will be gradually deformed. When the elongated hole 26 is deformed, the boosting effect by the handle member will be reduced.
Accordingly, an object of the present invention is to provide a boosting mechanism for a stapler which is free from the deformation by the force acting on the point of action and improved in durability.
To achieve the above object, there is provided a boosting mechanism for a stapler. In the boosting mechanism, bearing pieces are formed on both sides of the rear end of a clincher arm which includes a clincher table for bending a staple at the front end thereof. A magazine member, to which staples are loaded, and a driver arm for driving out a staple fed from the magazine member are pivotally mounted on an axle, which is provided at the rear ends of the bearing pieces. A handle member is rotatably disposed above the driver arm. A rotation supporting shaft of the handle member is provided at a position somewhat closer to the front than the axle of the bearing pieces. A pin, which is provided at a position closer to the front than the rotation supporting shaft of the handle member, is inserted into an elongated hole formed in each side plate of the driver arm.
Preferably, the boosting mechanism is constructed as follows:
The rotation supporting shaft is formed by burring the bearing pieces of the clincher arm. Engaging grooves to be brought into engagement with the rotation supporting shaft are formed in the handle member. Further, when the driver arm is driven to move in a staple driving direction by pressing the handle member, the rotation supporting shaft is brought into engagement with a semicircular front end of each of the engaging grooves.